Vancouver Avian Research Centre

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Species: Swainson's Thrush Catharus ustulatus

Description:

Swainson's Thrushes are a member of the Thrush family, in the Catharus genus with other similar looking North American thrushes. Two main subspecies groups exist; Pacific and Boreal. The Pacific have more russet colored upperparts, compared with more olive-brown upperparts in the Boreal populations.
It is well known for its flute-like upwardly spiraling song frequently heard at dusk and dawn during the breeding season. Swainson's Thrushes breed principally across the boreal forest from Alaska to Newfoundland, but also south through the Rocky and Coast Mountains. Their wintering range is through southern Mexico, Central America, and northern South America.

Identification:

General: Medium sized songbird. Adults measure about 17 cm long and weigh about 30 grams.

Adult: Sexes alike, although males are slightly larger than females. Warm brown upperparts, including tail and rump, with whitish underparts with black spotting in the throat and upper breast, legs pinkish, and bill pinkish with a black tip. Distinctive for Swainson's Thrushes are cream coloured eye-rings and lores giving a 'spectacles' look.

Juvenile: Similar to adults, however like all Catharus thrushes young birds.

Similar Species: Hermit Thrush has a reddish tail and rump and has and a whitish eye-ring. Gray-cheeked Thrush is a 'colder' brown colour, with a grayish cheek patch, and brown tail and rump. Veery generally has lighter brown upperparts, with brown tail and rump, mostly lacking an eye-ring, breast spots are more brownish or grayish and upper-breast washed with gray or light brown.

Behaviour: Generally inconspicuous on the forest floor or shrub layer. Forages by kicking up leaf litter and will more frequently fly-catch from shrubs than other thrushes. Usually hops along the ground, with its tail held upright, occasionally pumping its tail.

Habitat: Forest, including deciduous, mixed or coniferous. During the breeding season they are usually found in coniferous forest, typically spruce-fir forest, although they will use riparian forest in more southerly populations. In winter they frequent rainforest and second growth areas. During migration they are known to use a variety of habitats, but require a dense understory for protective cover.

Information:

Swainson's Thrushes, while primarily insect eaters during the breeding season, utilize late summer and fall berry crops to increase fat loads for migration and to provide additional energy during cold winter weather. Birds will frequent open or disturbed areas, such as bogs, clearcuts and burns to take advantage of high berry production in these areas. Frequently found in mixed species flocks during migration.
Swainson's Thrushes breed from April to June and typically have one brood per year, however two have been reported in some areas. Most clutches have four eggs, but known to vary between one and four, with an incubation period of 10-14 days, and fledging after 10-14 days.
During the breeding season most Catharus thrushes in BC segregate themselves by elevation or habitat. Swainson's Thrushes are found primarily in lower elevation forest and Hermit Thrushes in upper elevation forest in BC. Veery's, while found in low-land forest, are found in more riparian areas than Swainson's Thrushes.

Conservation Status: (Least Concern)

Populations are slightly decreasing throughout range. Some habitat loss on both the breeding and wintering grounds may be of concern, but large range and population size indicate overall it is fairly secure.
 
Capture Rates


Capture of Swainson’s Thrush begin in April as these long distance migrants arrive at Colony Farm from Central and South America. Capture rates (2010-2012; standardized as birds captured per 100 net hours) peak in August as young disperse from breeding areas of the mixed forest and brushy riparian habitat of Colony Farm.

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